Certain refrigerator appliances utilize sealed systems for cooling chilled chambers of the refrigerator appliances. A typical sealed system includes a compressor, a condenser, an expansion device, and an evaporator connected in series and charged with a refrigerant. The compressor continuously circulates refrigerant in the sealed system. In the condenser, hot, high pressure gas refrigerant condenses into liquid and expels heat. The liquid refrigerant passes through the expansion device where it rapidly expands and passes into the evaporator as a two-phase refrigerant. A fan may circulate air through the cold evaporator before delivering the cooled air through an opening into the chilled chamber. Air from the chilled chamber is circulated back through a return duct to be re-cooled by the sealed system. The process is repeated to maintain the chilled chamber at the desired temperature.
In some refrigerator appliances, a temperature controlled drawer may be positioned at the bottom of a fresh food chamber. The temperature controlled drawer may include controls to enable more precise control of the temperature within the drawer, and temperature sensitive foods may be placed in the drawer to prolong their shelf life. However, the location of the temperature controlled drawer within the fresh food chamber may lead to difficulty in maintaining a desired temperature within the drawer. For example, when the evaporator fan is turned off, cool air tends to settle near the bottom of the fresh food chamber, while hot air rises to the top.
In addition, the fresh food chamber evaporator is typically positioned just outside the bottom, back corner of the fresh food chamber. The evaporator may therefore be positioned immediately adjacent the temperature controlled drawer, and may cause undesirable or excessive cooling of the temperature controlled drawer. This is especially true in refrigerators equipped with dual evaporators connected in series—e.g., one for the fresh food chamber and one for the freezer chamber. During the freezer only cooling cycle, the fresh food evaporator stays cold because refrigerant is flowing, but no air is circulated through it. As a result, the temperature controlled drawer may get too cold due to conduction from the fresh food evaporator. For these reasons, the temperature controlled drawer is often the coldest portion of the fresh food chamber.
Conventional refrigerator appliances control the temperature of the temperature controlled drawer by using a fan and damper mechanism tied to the fresh food evaporator. When cooling is required, the damper opens to draw cold air from the evaporator into the temperature controlled drawer. When heating is required, a heater may be used to increase the temperature of the temperature controlled drawer. These configurations require additional components, more complicated assembly, and increased cost. Increased system complexity also leads to decreased reliability and increased service costs during the life of the refrigerator appliance.
Accordingly, a refrigerator appliance including a temperature controlled drawer having improved temperature control would be useful. More particularly, a refrigerator appliance enabling precise control of the temperature in the temperature controlled drawer independently of the operation of the fresh food evaporator would be especially beneficial.